Capacitive rotary encoder

ABSTRACT

A human machine interface includes a capacitive touch screen having a capacitive sensor. The capacitive touch screen displays text characters and/or graphical information. A control device is rotatably coupled to a structure such that the control device is superimposed over the screen. The control device includes at least one electrically conductive element. The control device rotates about an axis substantially perpendicular to the screen such that the at least one electrically conductive element follows the rotation of the control device. The capacitive sensor senses a rotational position of the at least one electrically conductive element.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.15/382,801, filed on Dec. 19, 2016, which currently wider allowance,which is a continuation of U.S. patent application Ser. No. 14/843,380,filed on Sep. 2, 2015, now U.S. Pat. No. 9,557,872, issued on Jan. 31,2017, which is a continuation of U.S. patent application Ser. No.13/715,330, filed on Dec. 14, 2012, now U.S. Pat. No. 9,158,422, issuedon Oct. 13, 2015, the disclosure of which is hereby incorporated byreference in its entirety for all purposes,

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to capacitive touch screens, and, moreparticularly, to a control device that is applied to a capacitive touchscreen.

2. Description of the Related Art

Current systems require discrete rotary encoders and additional supportcircuitry attached to a printed circuit board, and are not able to belocated over the active display area without obstructing the displayfrom view. This not only occupies valuable display area, but also limitsdesign freedom and the ability to dynamically assign and label thecontrol function.

Other inventions targeted toward the automotive industry includeprojection type displays and camera-based pattern recognition to decodethe controls which have been overlaid on the display surface. However,these known approaches have significantly higher costs than the presentinvention, and have yet to be automotive quail fled.

SUMMARY OF THE MENTION

The invention may include a mechanical rotary control device applied toa capacitive touch screen. Contacts on a control ring interact with acapacitive sensor which covers the display area on the display screen.Dynamic labels and/or control feedback may be displayed inside thecontrol ring. With the use of an appropriate multitouch controllerintegrated circuit (IC), multiple control rings may be supported.Mechanical detents may be molded into the control ring structure and/orinto the mechanical connection to the display lens in order to providetactile feedback regarding how far the control ring has been rotated(i.e., in angular degrees) by the user.

The invention comprises, in one form thereof, a human machine interfaceincluding a capacitive touch screen having a capacitive sensor. Thecapacitive touch screen displays text characters and/or graphicalinformation. A control device is rotatably coupled to a structure suchthat the control device is superimposed over the screen. The controldevice includes at least one electrically conductive element. Thecontrol device rotates about an axis substantially perpendicular to thescreen such that the at least one electrically conductive elementfollows the rotation of the control device. The capacitive sensor sensesa rotational position of the at least one electrically conductiveelement.

The invention comprises, in another form thereof, a method of operatinga human machine interface, including providing a capacitive touch screenhaving a capacitive sensor. A control device is superimposed over thescreen. The control device includes at least one electrically conductiveelement. The control device is rotatable about an axis substantiallyperpendicular to the screen such that the at least one electricallyconductive element follows the rotation of the control device. Textcharacters and/or graphical information are displayed on the capacitivetouch screen and adjacent to the control device. The text charactersand/or graphical information are indicative of a function of the controldevice. The capacitive sensor is used to sense a rotational position ofthe at least one electrically conductive element.

The invention comprises, in yet another form thereof, a human machineinterface including a capacitive touch screen having a capacitivesensor. The capacitive touch screen displays information to a user. Acontrol device is rotatably coupled to a structure such that the controldevice is superimposed over the screen. The control device rotates aboutan axis substantially perpendicular to the screen. The control deviceincludes a central viewing channel through which a user may view aportion of the information on the screen that is indicative of afunction of the control device. The control device includes at least oneelectrically conductive element that follows the rotation of the controldevice. The capacitive sensor senses a rotational position of the atleast one electrically conductive element.

An advantage of the present invention is that the touch screen may bere-programmable, and yet the advantages of a rotary dial are retained,such as tactile feedback and a fixed dial location which facilitatesmuscle memory.

Another advantage of the present invention is that it provides a welldefined hand gesture area in which the hand gestures may be reliablycaptured by a camera and recognized by use of a gesture recognitionalgorithm.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and objects of this invention,and the manner of attaining them, will become more apparent and theinvention itself will be better understood by reference to the followingdescription of embodiments of the invention taken in conjunction withthe accompanying drawings, wherein:

FIG. 1 is a plan view of one embodiment of a capacitive rotary encoderarrangement of the present invention.

FIG. 2 is a cross-sectional plan view of one of the capacitive rotaryencoders of the arrangement of FIG. 1.

FIG. 3a is a cross-sectional view of the arrangement of FIG. 1 in afirst position along line 3-3.

FIG. 3b is a cross-sectional view of the arrangement of FIG. 1 in asecond position along line 3-3.

FIG. 4 is an exploded view of another embodiment of a capacitive rotaryencoder suitable for use in the arrangement of FIG. 1.

FIG. 5 is an exploded view of yet another embodiment of a capacitiverotary encoder suitable for use in the arrangement of FIG. 1.

DETAILED DESCRIPTION

The embodiments hereinafter disclosed are not intended to be exhaustiveor limit the invention to the precise forms disclosed in the followingdescription. Rather the embodiments are chosen and described so thatothers skilled in the art may utilize its teachings.

FIG. 1 is a block diagram illustrating one embodiment of a human machineinterface in the form of a capacitive rotary encoder arrangement 10 ofthe present invention, which may be included in a motor vehicle, forexample. Arrangement 10 includes a rotary control overlay 12 disposedover, or superimposed over, a capacitive touch screen 14. Overlay 12includes a planar band 16 having opposite longitudinal ends attached toscreen 14. Band 16 may be a fixed structure that is formed of metal or arigid plastic material, for example. Band 16 includes three throughholeseach of which receives a respective annular capacitive rotary encoder orcontrol device in the form of a dial or knob 18 that is rotatablycoupled to band 16. Each of knobs 18 partially covers screen 14 andincludes a central, circular viewing channel 20 having a longitudinalaxis which is perpendicular to the page of FIG. 1. Viewing channel 20may be empty or may retain a glass or transparent plastic window. Thus,a user is able to view screen 14 through viewing channel 20. Each ofknobs 18 is rotatable in the plane of the page of FIG. 1, i.e., aboutits longitudinal axis, which is substantially perpendicular to screen14, in both a clockwise direction 22 and a counterclockwise direction24. Knobs 18 may include detents (not shown) in order to provide theuser with tactile feedback as he rotates the knob, as is well known withconventional automotive audio and HVAC knobs.

In one embodiment, knobs 18 do not include any wiring or electronics,but do include one or more capacitive contacts 26 (FIG. 2), which may bemade of any electrically conductive material, such as metal or carbonfiber. In the specific embodiment of FIG. 2, there are two capacitivecontacts 26 which are positioned to be diametrically opposed to eachother within annular knob 18.

As shown in FIGS. 3a-b in conjunction with FIG. 2, each of capacitivecontacts 26 may be rod-shaped with a longitudinal axis which isperpendicular to the pages of FIGS. 1 and 2. By being rod-shaped,contacts 26 may have a well defined or concentrated location relative tothe screen, and yet the relatively longer length of the rods indirections toward and away from screen 14 may provide enough physicalbulk to make contacts 26 easily sensed by a capacitive sensor, asdescribed below. Contacts 26 may not extend the entire longitudinallength of knob 18, but rather may be disposed on the longitudinal end ofknob 18 that is closer to screen 14, as shown in FIGS. 3a -b.

Capacitive touch screen 14 may include a capacitive sensor having amatrix of nodes 28 which are only fragmentarily shown in FIG. 1. Thematrix of nodes 28 may extend the entire length of screen 14, as shownin FIGS. 3a,b , as well as the entire width of screen 14. Nodes 28 mayeach sense a level of capacitance which may be affected by the distancebetween node 28 and one or both of contacts 26. Each of nodes 28 maytransmit a corresponding capacitance signal to a processor (not shown)which uses the capacitance signals to determine the locations ofcontacts 26 both in terms of rotational positions and in terns of thedistance between contacts 26 and screen 14 in general. That is, asillustrated by FIGS. 3a-b , knobs 18 may be pushed by the user from theposition in FIG. 3a to the position in FIG. 3b in which both knob 18 andhence contacts 26 are closer to screen 14. Thereby, the user mayactivate or select a menu selection or icon that is currently displayedon screen 14 through viewing channel 20. Knob 18 may be biased by aspring (not shown) back into the position of FIG. 3a after the usertakes his finger off of knob 18 and stops pushing knob 18 toward screen14.

Although knobs 18 are described with reference to FIGS. 3a-b as beingmovable in directions toward and away from screen 14, it is to beunderstood that the feature of knobs 18 being pushable is optional, andit is also possible for knobs 18 to be rotatable yet fixed in thedirection into the page of FIG. 1. In this case, each of nodes 28 maytransmit a corresponding capacitance signal to the processor which usesthe capacitance signals to determine the locations of contacts 26 onlyin terns of rotational positions relative to screen 14. Contacts 26 mayor may not touch or engage screen 14, and it is not necessary forcontacts 26 to touch screen 14 in order for the capacitive sensor tosense the positions of contacts 26. In one embodiment, there areapproximately between 750 and 800 nodes on screen 14, which may bearranged in a matrix of about thirty rows and twenty-five columns.

As shown in FIGS. 3a-b , one contact 26 may be closer to screen 14 thanthe other contact 26, and may extend toward screen 14 farther than theother contact 26, and thus the closer contact 26 may provide a higherlevel of capacitance than does the other contact 26. Thereby, theprocessor may differentiate between and/or identify each of the twocontacts 26. This may be useful in embodiments in which knob 18 has arange of rotational motion of at least 180 degrees, and it is thuspossible for either one of contacts 26 to be in a given position. Forinstance, the rotational position shown in FIG. 2 may correspond to amaximum sound volume, while a 180 degree rotation in counterclockwisedirection 24 corresponds to a minimum sound volume, with the twocontacts 26 effectively switching places in the two positions. By beingable to identify which contact 26 is which, the processor may determinewhether knob 18 is in the minimum volume position or the maximum volumeposition without having to reference any previous knob positioninformation.

Illustrated in FIG. 4 is an exploded view of another embodiment of acapacitive rotary encoder 118 suitable for use in the arrangement ofFIG. 1. As in the embodiment of FIGS. 1-3, capacitive rotary encoder 118is in the form of a knob. Capacitive rotary encoder 118 includes anannular cap 130 with an open center 132. Received in cap 130 is a wavespring 134 including a projection 136 and two diametrically opposed legs138. Two capacitive contacts 126 are each attached to a distal end of arespective leg 138. A fixed planar ring 140 includes circumferentiallyspaced notches 142 for engaging projection 136 and providing tactilefeedback as cap 130 is rotated and projection 136 rotates from notch tonotch.

Illustrated in FIG. 5 is an exploded view of yet another embodiment of acapacitive rotary encoder 218 suitable for use in the arrangement ofFIG. 1. As in the embodiments of FIGS. 14, capacitive rotary encoder 218is in the form of a knob. Capacitive rotary encoder 218 includes anannular cover or cap 230 with an open center 232. Received in cap 230,or formed integrally with cap 230, are two diametrically opposedhurricane springs 234. Each hurricane spring 234 spans about ninetydegrees in circumferential directions. At a distal end of each hurricanespring 234 is a radially extending projection 233. Also received in cap230, or formed integrally with cap 230, are two diametrically opposedfemale snaps 235. Each female snap 235 spans about ninety degrees incircumferential directions. A contact carrier 236 includes twodiametrically opposed male snaps 237, each of which snaps into arespective one of female snaps 235. Each male snap 237 spans aboutninety degrees in circumferential directions. Contact carrier 236 alsoincludes two through holes 238 a-b, each of which receives a respectiveone of contacts 240 a-b. Contacts 240 a-b are electrically connected bya contact bridge 242. A mounting ring 244 is received in cap 230 andincludes radially inwardly-facing detents 246 which engage projections233 of hurricane springs 234. Mounting ring 244 includes three mountingholes 245 by which ring 244 may be fixed relative to screen 14 such thatcap 230 and contact carrier 236 are rotatable relative to ring 244.Detents 246 and projections 233 may cooperate to provide tactilefeedback as cap 230 is rotated and projections 233 engage detents 246.

During use, text characters and/or graphical information such as iconsmay be displayed on screen 14 and may be viewable through viewingchannels 20 to indicate the purpose, function or applicationcorresponding to each of knobs 18, such as audio volume, radiofrequency, HVAC temperature, fan speed, etc. In one embodiment, the modeor purpose of a knob 18 may be toggled or switched, via software, bypushing and releasing the knob. For example, pushing and releasing knob18 may toggle the knob between audio volume and radio frequency, and thetext characters and/or icon displayed within the knob's viewing channelmay change accordingly. Thus, the invention allows for dynamicrelabeling of the control by use of a graphical human machine interface(HMI) including screen 14.

Knobs 18 are shown as being held by band 16 in a same row across screen14, however, it is to be understood that the knobs do not have to be ina same row or column within the scope of the invention. Rather, theknobs can be in any places relative to each other and relative to screen14.

Screen 14 is shown in FIGS. 3a-b as having a concave shape. However, itis to be understood that screen 14 may have other shapes within thescope of the invention, e.g., flat or planar.

Although band 16 is described as being fixed, it is also possible forband 16 to be movable. For example, band 16 may be slidable indirections up and down the page of FIG. 1 such that knobs 18 may beplaced over different menu selections on screen 14.

In another embodiment (not shown), a slider including a capacitivecontact is slidable along one of the four edges of a rectangularcapacitive screen. Capacitive sensor nodes along the edge of the screenmay sense the location of the capacitive contact within the slider.Thus, the present invention may be applied to any movable control inorder to sense the position of the control without the need for wiringor electronics.

In yet another embodiment (not shown), the present invention is appliedto a resistive touch screen instead of a capacitive touch screen.Multi-touch support is possible for a resistive touch screen, but maydepend upon even pressure being applied to the resistive touch screenfor accurate gesture detection. By careful tuning of the mechanicalforce applied to the encoder contact points, accurate gesture detectionmay be achieved for a resistive touch screen that is able to supportmulti-touch inputs.

While this invention has been described as having an exemplary design,the present invention may be further modified within the spirit andscope of this disclosure. This application is therefore intended tocover any variations, uses, or adaptations of the invention using itsgeneral principles. Further, this application is intended to cover suchdepartures from the present disclosure as come within known or customarypractice in the art to which this invention pertains.

What is claimed is:
 1. A human machine interface comprising: acapacitive touch screen including a capacitive sensor, the capacitivetouch screen being configured to display text characters and/orgraphical information; and a control device rotatably coupled to astructure such that the control device is superimposed over the screen,the control device including at least one electrically conductiveelement, the control device being configured to rotate about an axissubstantially perpendicular to the screen such that the at least oneelectrically conductive element follows the rotation of the controldevice; wherein the capacitive sensor is configured to sense arotational position of the at least one electrically conductive element;and wherein the control device is actuatable in directions toward andaway from the screen such that the at least one electrically conductiveelement follows the movement toward and away from the screen, thecapacitive sensor being configured to sense a position of the at leastone electrically conductive element in the directions toward and awayfrom the screen without the control device touching the screen.
 2. Theinterface of claim 1 wherein the control device comprises a knob.
 3. Theinterface of claim I wherein the screen is configured to displayinformation adjacent to the control device, the information beingindicative of a function of the control device.
 4. The interface ofclaim 3 wherein the control device includes a central viewing channelthrough which a user may view the information on the screen.
 5. Theinterface of claim 1 wherein the structure comprises a planar bandextending across the screen.
 6. The interface of claim 1 wherein thecontrol device includes a wave spring with two diametrically opposedlegs, a respective said electrically conductive element being attachedto a distal end of each of the legs.
 7. The interface of claim 1 whereinthe at least one electrically conductive element comprises a firstelectrically conductive element and a second electrically conductiveelement, the first electrically conductive element being closer to thescreen than is the second electrically conductive element, thecapacitive sensor being configured to sense that the first electricallyconductive element is closer to the screen than is the secondelectrically conductive element.
 8. A method of operating a humanmachine interface, comprising the steps of: providing a capacitive touchscreen including a capacitive sensor; superimposing a control deviceover the screen, the control device including at least one electricallyconductive element, the control device being rotatable about an axissubstantially perpendicular to the screen such that the at least oneelectrically conductive element follows the rotation of the controldevice; displaying text characters and/or graphical information on thecapacitive touch screen and adjacent to the control device, the textcharacters and/or graphical information being indicative of a functionof the control device; using the capacitive sensor to sense a rotationalposition of the at least one electrically conductive element; and usingthe capacitive sensor to sense actuation of the control device indirections toward and away from the screen such that the at least oneelectrically conductive element follows the movement toward and awayfrom the screen, the capacitive sensor sensing positions of the at leastone electrically conductive element in the directions toward and awayfrom the screen while the control device is spaced apart from thescreen.
 9. The method of claim 8 comprising the further step ofadjusting an operating parameter of an audio system, an HVAC system, ora navigation system of a motor vehicle, the adjusting being dependentupon the sensed rotational position.
 10. The method of claim 8comprising the further step of displaying information on the screenadjacent to the control device.
 11. The method of claim 10 wherein theinformation is indicative of a function of the control device.
 12. Themethod of claim 11 wherein the control device includes a central viewingchannel, the displaying step including displaying the information on thescreen such that the information is visible through the central viewingchannel.
 13. The method of claim 8 comprising the further step ofsupporting the control device over the screen by use of a planar bandextending across the screen.
 14. The method of claim 8 comprising thefurther steps of: providing the control device with a wave spring withtwo diametrically opposed legs, a respective said electricallyconductive element being attached to a distal end of each of the legs;and using the control device to provide a user with tactile feedback inresponse to the user rotating the control device about the axis.
 15. Ahuman machine interface comprising: a capacitive touch screen includinga capacitive sensor, the capacitive touch screen being configured todisplay information; and a control device rotatably coupled to astructure such that the control device is superimposed over the screen,the control device being configured to rotate about an axissubstantially perpendicular to the screen, the control device includinga central viewing channel through which a user may view a portion of theinformation on the screen that is indicative of a function of thecontrol device, the control device including at least one electricallyconductive element that follows the rotation of the control device;wherein the capacitive sensor is configured to sense a rotationalposition of the at least one electrically conductive element; andwherein the control device is actuatable in directions toward and awayfrom the screen such that the at least one electrically conductiveelement follows the movement toward and away from the screen, thecapacitive sensor being configured to sense a position of the at leastone electrically conductive element in the directions toward and awayfrom the screen with the control device remaining in disengagement fromthe screen.
 16. The interface of claim 15 wherein the control devicecomprises a knob.
 17. The interface of claim 15 wherein the structurecomprises a planar band extending across the screen.
 18. The interfaceof claim 15 wherein the control device includes a wave spring with twodiametrically opposed legs, a respective said electrically conductiveelement being attached to a distal end of each of the legs.
 19. Theinterface of claim 15 wherein the control device comprises an annularknob, the central viewing channel having a circular cross section. 20.The interface of claim 15 wherein the at least one electricallyconductive element comprises a first electrically conductive element anda second electrically conductive element, the first electricallyconductive element being diametrically opposed to the secondelectrically conductive element, the first electrically conductiveelement being closer to the screen than is the second electricallyconductive element, the capacitive sensor being configured to sense:that the first electrically conductive element is closer to the screenthan is the second electrically conductive element; and the respectiverotational positions of the first electrically conductive element andthe second electri